1. Field of the Invention
This invention relates to an apparatus and a method for detecting mass eccentricity of a spherical object such as a golf ball.
2. Description of the Related Art
Mass eccentricity of an object is generated by deformation of external shape, local defects of surface, and internal defects (such as air inclusion). And, in case that the object comprises plural layers of different specific gravity, mass eccentricity is also generated by ununiformity of thickness of each layer.
As methods for detecting these, visual examination and dimension measurement have been practiced in deformation of external shape and defects of the surface. For internal defects and ununiformity of thickness of each layer in a multilayer structure which includes plural layers of different specific gravity, in case of non-destructive examination, X-ray image observation and supersonic wave measurement have been practiced, and in case of destructive examination, measurement of cross section has been practiced. That is to say, these methods do not measure the mass eccentricity itself but detect causes of generation.
In case that the causes of the mass eccentricity are internal defects and ununiformity of thickness of each layer in the multilayer structure which includes plural layers of different specific gravity, however, positions of the internal defects and mass eccentricity caused by the internal defects are not known quantitatively, since only permeation speed is observed in the supersonic wave measurement. Although the internal defects and the mass eccentricity can be known with the X-ray image observation in some cases, in case that material near the surface of the examined object includes atoms of high X-ray absorptivity, obtaining quantitative information of the internal defects and the mass eccentricity is difficult, since obtaining good X-ray images is difficult.
Further, in these cases, it is difficult to directly know influences of mass eccentricity of a rotating product in actual use, because the causes of mass eccentricity generation are detected individually and the mass eccentricity is not measured in totality.
It is therefore an object of the present invention to provide an apparatus and a method for detecting mass eccentricity which can easily and surely detect mass eccentricity of a product which rotates in actual use (a golf ball etc.) in totality.